Hydrophobic-hydrophilic Interface Research Articles

Boron Cluster Anions Dissolve En Masse in Lipids Causing Membrane Expansion and Thinning.

Boron clusters are applied in medicinal chemistry because of their high stability in biological environments and intrinsic ability to capture neutrons. However, their intermolecular interactions with lipid membranes, which are critical for their cellular delivery and biocompatibility, have not been comprehensively investigated. In this study, we combine different experimental methods - Langmuir monolayer isotherms at the air-water interface, calorimetry (DSC, ITC), and scattering techniques (DLS, SAXS) - with MD simulations to evaluate the impact of closo-dodecaborate clusters on model membranes of different lipid composition. The cluster anions interact strongly with zwitterionic membranes (POPC and DPPC) via the chaotropic effect and cause pronounced expansions of lipid monolayers. The resulting lipid membranes contain up to 33 mol % and up to 52 weight % of boron cluster anions even at low aqueous cluster concentrations (1 mM). They show high (μM) affinity to the hydrophilic-hydrophobic interface, affecting the structuring of the lipid chains, and therefore triggering a sequence of characteristic effects: (i) an expansion of the surface area per lipid, (ii) an increase in membrane fluidity, and (iii) a reduction of bilayer thickness. These results aid the design of boron cluster derivatives as auxiliaries in drug design as well as transmembrane carriers and help rationalize potential toxicity effects.

DMF-Bimol: Counting mRNA and Protein Molecules in Single Cells with Digital Microfluidics.

Analyzing single-cell protein and mRNA levels yields invaluable insights into cellular functions and the intricacies of biologically heterogeneous systems. Current joint mRNAs and protein analysis methodologies suffer from relative quantification, low sensitivity, possible background interference, and tedious manual manipulation. Therefore, we propose DMF-Bimol that leverages addressable digital microfluidics to automate digital counting of single-cell mRNA and protein based on proximity ligation assay (PLA) and one-step RT-droplet digital PCR (RT-ddPCR). Through an engineered hydrophilic-hydrophobic interface, DMF-Bimol enables efficient single-cell isolation and lossless protein and nucleic acid processing. The closed droplet reaction system enhances the protein concentration and isolates exogenous contaminants, thereby dramatically improving the efficiency of the PLA reaction. The limit of detection of this approach achieves 3313 protein copies, marking a significant 17-fold enhancement in sensitivity over traditional benchtop PLA. This heightened sensitivity also uncovers a lower correlation between mRNA and protein levels in individual cells (Spearman r = 0.255) than bulk results, reflecting the complex relationship in heterogeneous cells. Using DMF-Bimol, we observed a significant upsurge of CD147 protein in CD138+ myeloma cells but consistent levels of CD147 mRNAs compared with normal leukocytes. This discovery indicates a possible consequence of CD147 oncogenic activation that tends to harness protein translation to bolster tumor cell survival and enhance invasiveness, highlighting the potential of DMF-Bimol in unveiling intricate dynamics in translation processes at the single-cell level.

Enhancement of carbonation, water purification and CO2 self-sequestration in hydrophobic piezo-photocatalytic carbonation coating for concrete

A eco-friendly carbonation coating (HBCC) with a piezo-photocatalysis was developed using gamma-dicalcium silicate and hydrophobic BiOI/BaTiO3 (HB), aiming at purifying pollutants by multi-dimensional energy (mechanical energy and visible light) and self-sequestrating CO2 produced by degrading pollutants. Based on the self-floating effect induced by the hydrophobicity of HB, the increase of catalyst content on the surface of HBCC was studied to promote the formation of a hydrophilic-hydrophobic interface. The selective adsorption of CO2 and H2O molecules by the hydrophilic-hydrophobic interface of HBCC was confirmed by simulations and experiments, which accelerates carbonation. Also, carbonation degree (37.1 %), bonding strength (40.1 %), and anti-corrosion performance (15.4 %) enhanced induced by accelerating carbonation was further confirmed. Additionally, HBBC exhibits the prominent degradation effect of Rhodamine b (90.8 %), methylene blue (86.6 %), and sulfamethoxazole (74.7 %) under ultrasound and visible light within 60 min. Meanwhile, CO2 emitted by piezo-photocatalytic degradation pollutants can be efficient sequestration by HBCC itself, and the carbonation can be enhanced to further improve its bonding strength. Finally, the enhancement mechanism of carbonation, water purification, and CO2 self-sequestration of HBBC was explored and ascertained.

Beetle-inspired AuNPs semi-embedded colloidal crystal chips for the highly sensitive and colored detection of chloramphenicol in foods

Inspired by the desert beetle, a novel biomimetic chip was developed to detect chloramphenicol (CP). The chip was characterized by a periodic array in which hydrophobic Au nanoparticles (AuNPs) were semi-embedded on hydrophilic polymethyl methacrylate (PMMA) spheres. Among them, the AuNPs exhibited both a localized surface plasmon resonance effect to amplify the reflected signal and a synergistic effect with PMMA spheres to create a significant hydrophilic-hydrophobic interface, which facilitated the enrichment of target CP molecules and improved sensitivity. After optimization, the chip showed direct, ultrasensitive (as low as 0.2 ng/mL), fast (5 min), and selective detection of CP with a wide concentration range extending from 0.2 ng/mL to 1000 ng/mL. During detection, color changes of the chip were observed by naked eyes without any color display equipment. The recovery of CP was between 94.65 % and 108.70 % in chicken and milk samples.

Multifunctional laser-induced graphene circuits and laser-printed nanomaterials toward non-invasive human kidney function monitoring

Faced with the increasing prevalence of chronic kidney disease (CKD), portable monitoring of CKD-related biomarkers such as potassium ion (K+), creatinine (Cre), and lactic acid (Lac) levels in sweat has shown tremendous potential for early diagnosis. However, a rapidly manufacturable portable device integrating multiple CKD-related biomarker sensors for ease of sweat testing use has yet to be reported. Here, a portable electrochemical sensor integrated with multifunctional laser-induced graphene (LIG) circuits and laser-printed nanomaterials based working electrodes fabricated by fully automatic laser manufacturing is proposed for non-invasive human kidney function monitoring. The sensor comprises a two-electrode LIG circuit for K+ sensing, a three-electrode LIG circuit with a Kelvin compensating connection for Cre and Lac sensing, and a printed circuit board based portable electrochemical workstation. The working electrodes containing Cu and Cu2O nanoparticles fabricated by two-step laser printing show good sensitivity and selectivity toward Cre and Lac sensing. The sensor circuits are fabricated by generating a hydrophilic-hydrophobic interface on a patterned LIG through laser. This sensor recruited rapid laser manufacturing and integrated with multifunctional LIG circuits and laser-printed nanomaterials based working electrodes, which is a potential kidney function monitoring solution for healthy people and kidney disease patients.

Elastic, Janus 3D evaporator with arch-shaped design for low-footprint and high-performance solar-driven zero-liquid discharge

Solar-driven zero-liquid discharge (ZLD) is a promising wastewater management strategy for freshwater recovery and solid waste harvesting. However, practical application of the solar-driven ZLD is severely constrained due to its low evaporation efficiency, large footprint, and rapid salt accumulation. Here, we present a Janus arch-shaped solar-driven evaporator (▪) comprising a hydrophobic top photothermal layer for effective light absorption, solar-thermal conversion, and vapor evaporation, which exhibits an evaporation rate of 2.82 kg∙m−2∙h−1 in pure water. The design also includes shapable delignified longitudinal wood (D-L-wood) serving as the hydrophilic bottom water transport layer, which enables dual-directional saltwater transportation and salt crystallization. D-L-wood, with numerous aligned channels, exhibits a low thermal conductivity of 0.04 W·m−1·K−1 along perpendicular direction and can effectively localize heat on the photothermal layer of the evaporator. D-L-wood has excellent hydrophilicity, and the salty water can be transferred quickly along both ends of the wood, providing sufficient salty water for rapid evaporation. The anisotropy of the wood makes the heat transfer quickly along the channel, improving the thermal management ability of the evaporator. Moreover, during vapor evaporation on the hydrophilic-hydrophobic interface, salt is crystallized at the hydrophilic layer, resulting in an enhanced anti-salt performance, a 1.5 folds evaporation rate compared with non-Janus evaporator after 15 h test. Under the conditions of a salt concentration of 3.5 %, a high salt harvest performance of 62.4 g∙m−2∙h−1 can be obtained under AM 1.5 solar irradiation. The arch-shaped design fully utilizes the upper space and effectively reduces evaporator footprint, resulting in an evaporation area to footprint ratio of 1.57:1. The designed evaporator can also be utilized for ZLD treatment of other heavy metal polluted water including Cu2+, CrO42−, Co2+, and so on. Therefore, the Janus-arch-shaped, solar-driven evaporator enables a potentially low-footprint, low-cost, scalable, and practical ZLD strategy for sustainable wastewater treatment.

Biosurfactants as templates to inspire new environmental and health applications

Life exists at an interface. One of the key characteristics of biological cells is compartmentalization, which is facilitated by lipids that create a water-impenetrable barrier to control transport of materials across the hydrophilic-hydrophobic interface. Microbial systems utilize a rich diversity of surfactants beyond lipids to adapt to an environmental niche, modify the properties of an interface, facilitate solubilization of nutrients for metabolism and as antimicrobials. As such, they are a fascinating class of biomolecules to study in terms of how effectiveness in an application or niche environment depends on sequence, structure and chemical properties. Moreover, there is increasing appreciation of the negative health and environmental impacts petrochemical-based surfactants can have, such as soil erosion and toxicity to plants and aquatic life, as well as the carbon footprint and associated greenhouse gas emissions associated with petrochemical surfactant manufacturing. In this review, we discuss the properties of biosurfactants and applications, and highlight key glycolipid-, protein- and peptide-based surfactants described in literature as examples of biosurfactants with unique potential and applications. As society looks towards the transition to a circular bioeconomy, we are excited by the potential of synthetic biology to develop new materials such as biosurfactants to facilitate this important transition.

Well-Defined Shell-Sheddable Core-Crosslinked Micelles with pH and Oxidation Dual-Response for On-Demand Drug Delivery.

Micellar-nanocarrier-based drug delivery systems possessing characteristics such as an excellent circulation stability, inhibited premature release and on-demand site-specific release are urgently needed for enhanced therapeutic efficacy. Therefore, a novel kind of shell-sheddable core-crosslinked polymeric micelles with pH and oxidation dual-triggered on-demand drug release behavior was facilely constructed. The multifunctional micelles were self-assembled from a carefully designed amphiphilic triblock PEGylated polyurethane (PEG-acetal-PUBr-acetal-PEG) employing an acid-labile acetal linker at the hydrophilic-hydrophobic interface and pendant reactive bromo-containing polyurethane (PU) as the hydrophobic block, followed by a post-crosslinking via oxidation-cleavable diselenide linkages. These well-defined micelles exhibited an enhanced structural stability against dilution, achieved through the incorporation of diselenide crosslinkers. As expected, they were found to possess dual pH- and oxidation-responsive dissociation behaviors when exposure to acid pH (~5.0) and 50 mM H2O2 conditions, as evidenced using dynamic light-scattering (DLS) and atomic force microscopy (AFM) analyses. An in vitro drug release investigation showed that the drug indomethacin (IND) could be efficiently encapsulated in the micelles, which demonstrated an inhibited premature release compared to the non-crosslinked ones. It is noteworthy that the resulting micelles could efficiently release entrapped drugs at a fast rate in response to either pH or oxidation stimuli. Moreover, the release could be significantly accelerated in the presence of both acid pH and oxidation conditions, relative to a single stimulus, owing to the synergetic degradation of micelles through pH-induced dePEGylation and oxidation-triggered decrosslinking processes. The proposed shell-sheddable core-crosslinked micelles with a pH and oxidation dual-response could be potential candidates as drug carriers for on-demand drug delivery.

Hydrophilic-hydrophobic heterogeneous interface enables the formation of a high-performance polyamide membrane for water purification

Polyamide reverse osmosis (RO) membranes possessing high water permeance and high salt rejection are highly beneficial for efficient desalination and wastewater treatment. However, achieving desired membrane properties toward both fast water transport and outstanding salt rejection remains a great challenge. Herein, we report the fabrication of high-performance polyamide RO membrane via interfacial polymerization (IP) on a heterogeneous substrate featuring a hydrophobic surface and polyaniline modified hydrophilic pores. The heterogeneous substrate, combining the advantages of conventional hydrophilic and hydrophobic substrates for IP process, leads to the formation of an ultra-thin polyamide film with rough morphology. The obtained RO membranes thereby not only have simultaneously enhanced water permeance (3.28 L m−2h−1 bar−1) and salt rejection (NaCl rejection 99.5 %), but also exhibit outstanding pH stability, anti-fouling performance, and long-term stability. In addition, the regulation mechanism of the heterogeneous substrate on IP was comprehensively investigated by combing molecular simulation and experiments. Our work provides a novel design direction of substrate used for fabricating RO membrane with outstanding performance.

Hydrophobic-hydrophilic Alternation: An effective Pattern to de novo Designed Antimicrobial Peptides.

The antimicrobial peptide (AMP) is a class of molecules that are active against a variety of microorganisms, from bacterial and cancer cells to fungi. Most AMPs are natural products, as part of an organism's own defense system against harmful microbes. However, the growing prevalence of drug resistance has forced researchers to design more promising engineered antimicrobial agents. Inspired by the amphiphilic detergents, the hydrophobic-hydrophilic alternation pattern was considered to be a simple but effective way to de novo design AMPs. In this model, hydrophobic amino acids (leucine, isoleucine etc.) and hydrophilic amino acids (arginine, lysine etc.) were arranged in an alternating way in the peptide sequence. The majority of this type of peptides have a clear hydrophilic-hydrophobic interface, which allows the molecules to have good solubility in both water and organic solvents. When they come into contact with hydrophobic membranes, many peptides undergo a conformational transformation, facilitating themself to insert into the cellular envelope. Moreover, positive-charged peptide amphiphiles tended to have an affinity with negatively-charged membrane interfaces and further led to envelope damage and cell death. Herein, several typical design patterns have been reviewed. Though varying in amino acid sequence, they all basically follow the rule of alternating arrangement of hydrophilic and hydrophobic residues. Based on that, researchers synthesized some lead compounds with favorable antimicrobial activities and preliminarily investigated their possible mode of action. Besides membrane disruption, these AMPs are proven to kill microbes in multiple mechanisms. These results deepened our understanding of AMPs' design and provided a theoretical basis for constructing peptide candidates with better biocompatibility and therapeutic potential.

Electrospun nanofibrous membranes with asymmetric wettability for unidirectional moisture transport, efficient PM capture and bacteria inhibition

The performance of moisture management, PM capture, and bacteria inhibition are significant for air cleaning materials. Herein, a nanofiber composite PVDF/PAN-CTAB membrane with multiple functions was constructed via a facile electrospinning strategy. Incorporating cetyltrimethyl ammonium bromide (CTAB) in the windward PAN layer simultaneously improved membrane moisture transport rate, antibacterial performance, and PM capture ability. The enhanced moisture management performance was achieved by regulating the microstructure of the nanofibers and the thickness ratio of the asymmetric wetting layers. Hydrophobic-hydrophilic interface superimposed force on water droplets was measured to thoroughly investigate directional water transport behavior. Consequently, the prepared PVDF/PAN-CTAB membrane possesses a water vapor transport rate of >13 kg m−2 d−1, PM0.3 removal efficiency of ≥99% with a low pressure drop of ∼84 Pa, and an E. coli inhibition rate of 99.99%. This work would pave the way for engineering asymmetric wettability structure to improve the moisture management performance of antibacterial air cleaning membrane, and provides a novel scientific sight on directional water transport phenomenon based on force test and analysis.

Micellar interface modulation self-assembly strategy towards mesoporous bismuth oxychloride-based materials for boosting photocatalytic pharmaceuticals degradation

The spontaneous recombination of photogenerated carriers greatly limits the improvement of photocatalytic efficiency for bismuth oxychloride-based catalysts. Constructing porous or heterostructure photocatalysts can effectively inhibit their recombination. However, owing to the fast hydrolysis/condensation rates and uncontrollable nucleation/growth kinetics of Bi3+ species, it is difficult to achieve inorganic–organic co-assembly, and form mesoscopic structure and heterostructure. Herein, a series of mesoporous bismuth oxychloride-based materials (Bi2O3 at a stoichiometric ratio of 0 for Cl, Bi12O17Cl2, heterostructured Bi12O17Cl2/BiOCl and BiOCl) with various stoichiometry, tunable compositions and large surface areas are synthesized by a micellar interface modulation self-assembly strategy. In this strategy, Pluronic P123 and cetyltrimethyl ammonium chloride (CTAC) form P123/CTA+ composite micelles, which assemble with Bi3+ precursors by Coulomb interactions. Moreover, the Cl- ions are induced and modulated through composite micelles to involve in the slow hydrolysis and condensation of Bi3+ precursors at the hydrophilic-hydrophobic interface of composite micelles to form mesophase, thereby realizing the synthesis of mesoporous bismuth oxychloride with various stoichiometry and compositions by regulating CTAC amount. The prepared mesoporous Bi12O17Cl2/BiOCl-OV shows superior photocatalytic activity (degrade 83% within 30 min for 10 mg/L carbamazepine and 99% within 10 min for 10 mg/L ciprofloxacin), which can be ascribed to the mesoporous architecture, intimate contact heterojunction and abundant surface oxygen vacancies. This work provides a new idea and strategy for design and synthesis of high-efficiency mesoporous bismuth oxychloride-based photocatalysts.

Umbrella Sampling Simulations of Carbon Nanoparticles Crossing Immiscible Solvents.

We use molecular dynamics to compute the free energy of carbon nanoparticles crossing a hydrophobic–hydrophilic interface. The simulations are performed on a biphasic system consisting of immiscible solvents (i.e., cyclohexane and water). We solvate a carbon nanoparticle into the cyclohexane layer and use a pull force to drive the nanoparticle into water, passing over the interface. Next, we accumulate a series of umbrella sampling simulations along the path of the nanoparticle and compute the solvation free energy with respect to the two solvents. We apply the method on three carbon nanoparticles (i.e., a carbon nanocone, a nanotube, and a graphene nanosheet). In addition, we record the water-accessible surface area of the nanoparticles during the umbrella simulations. Although we detect complete wetting of the external surface of the nanoparticles, the internal surface of the nanotube becomes partially wet, whereas that of the nanocone remains dry. This is due to the nanoconfinement of the particular nanoparticles, which shields the hydrophobic interactions encountered inside the pores. We show that cyclohexane molecules remain attached on the concave surface of the nanotube or the nanocone without being disturbed by the water molecules entering the cavity.

Effect of Functional Group on the Catalytic Activity of Lipase B from Candida antarctica Immobilized in a Silica-Reinforced Pluronic F127/α-Cyclodextrin Hydrogel

Surface modification plays a key role in the fabrication of highly active and stable enzymatic nanoreactors. In this study, we report for the first time the effect of various functional groups (epoxy, amine, trimethyl, and hexadecyl) on the catalytic performance of lipase B from Candida antarctica (CALB) incorporated within a monolithic supramolecular hydrogel with multiscale pore architecture. The supramolecular hydrogel formed by host-guest interactions between α-cyclodextrin (α-CD) and Pluronic F127 was first silicified to provide a hierarchically porous material whose surface was further modified with different organosilanes permitting both covalent anchoring and interfacial activation of CALB. The catalytic activity of nanoreactors was evaluated in the liquid phase cascade oxidation of 2,5-diformylfuran (DFF) to 2,5-furandicarboxylic acid (FDCA) under mild conditions. Results showed that high FDCA yields and high efficiency conversion of DFF could be correlated with the ability of epoxy and amine moieties to keep CALB attached to the carrier, while the trimethyl and hexadecyl groups could provide a suitable hydrophobic-hydrophilic interface for the interfacial activation of lipase. Cationic cross-linked β-CD was also evaluated as an enzyme-stabilizing agent and was found to provide beneficial effects in the operational stability of the biocatalyst. These supramolecular silicified hydrogel monoliths with hierarchical porosity may be used as promising nanoreactors to provide easier enzyme recovery in other biocatalytic continuous flow processes.

Molecular Basis for the Morphological Transitions of Surfactant Wormlike Micelles Triggered by Encapsulated Nonpolar Molecules.

Surfactant wormlike micelles are prone to experience morphological changes, including the transition to spherical micelles, upon the addition of nonpolar additives. These morphological transitions have profound implications in diverse technological areas, such as the oil and personal-care industries. In this work, additive-induced morphological transitions in wormlike micelles were studied using a molecular theory that predicts the equilibrium morphology and internal molecular organization of the micelles as a function of their composition and the molecular properties of their components. The model successfully captures the transition from wormlike to spherical micelles upon the addition of a nonpolar molecule. Moreover, the predicted effects of the concentration, molecular structure, and degree of hydrophobicity of the nonpolar additive on the wormlike-to-sphere transition are shown to be in good agreement with experimental trends in the literature. The theory predicts that the location of the additive in the micelle (core or hydrophobic-hydrophilic interface) depends on the additive hydrophobicity and content, and the morphology of the micelles. Based on the results of our model, simple molecular mechanisms were proposed to explain the morphological transitions of wormlike micelles upon the addition of nonpolar molecules of different polarities.

Exploring the Structural Stability and Assembly Mechanism of Hydrophobin Proteins

Hydrophobins are small, globular proteins with amphiphilic character that are produced and secreted by filamentous fungi. At hydrophobic-hydrophilic interfaces they self-assemble into durable amyloid-containing structures, called rodlets, which create protective, water repellent coatings for fungal spores. Current models of hydrophobin self-assembly predict that hydrophobin monomers undergo a conformational change at a hydrophobic-hydrophilic interface and integrate into a growing rodlet, however the mechanistic details of rodlet assembly are unknown.

Enhanced ion conductivity of sulfonated poly(arylene ether sulfone) block copolymers linked by aliphatic chains constructing wide-range ion cluster for proton conducting electrolytes

A series of sulfonated poly(arylene ether sulfone) block copolymers with aliphatic chains (SPAES-LA) to lend structural flexibility in the polymer backbone have been synthesized to prepare proton exchange membranes (PEMs) showing improved electrochemical performance and dimensional/oxidative stabilities. The SPAES-LAs, bearing different hydrophilic/hydrophobic segment lengths, are prepared via polycondensation and sulfonation reactions. The sulfonation reaction occurs in specific fluorenylidene units by using chlorosulfonic acid. The SPAES-LA membrane, fabricated by solvent casting method, exhibits remarkable dimensional/thermal stabilities. Moreover, proton conductivity of as-prepared SPAES-LA membranes demonstrates significant improvement with expansion of ion clusters which is due to the increased hydrophilic volume ratio. In particular, the SPAES-LA-X12Y28 membrane exhibited heightened proton conductivity of 158.4 mS cm−1 as well as suitable dimensional stability and durability towards radical oxidation, due to an effective well-defined hydrophilic-hydrophobic interface. Furthermore, H2/O2 fuel cell performance using SPAES-LA-X12Y28 membrane achieves a maximum power density of 232.02 mW cm−2, a result which points out that SPAES-LA membranes show great potential for applications of polymer electrolyte membrane.

Pool boiling enhancement on biphilic micropillar arrays: Control on the thin film evaporation and rewetting flow

In the present article, a new surface treatment is proposed for pool boiling enhancement. For this purpose, a combination of hydrophilic–hydrophobic micropillar arrays with hydrophilic insulation strips between them is used to control and manage the thin film evaporation, surface rewetting, and bubble dynamics. The distance between hydrophobic sections of micropillars acts as permanent active nucleation site for pool boiling, which liquid thin films are established at the hydrophilic–hydrophobic interface. The hydrophilic section of micropillars is used for surface rewetting based on the wicking mechanism. The bubble dynamics is controlled by insulation strips to avoid the merging of departure bubbles and also vapor jets and columns. The effect of micropillar array dimensions on the pool boiling is investigated for the case of water on the hybrid silicon micropillar array. The maximum heat flux is 377.5 W/cm2 at 10 K wall superheat. Moreover, the variation of boiling heat flux is almost linear with respect to the wall superheat due to the permanent active nucleation sites. It leads to significant pool boiling enhancement at low superheat temperatures.

Twisted Eigen Can Induce Proton Transfer at a Hydrophobic-Hydrophilic Interface.

The investigation of proton localization at a hydrophobic-hydrophilic interface is an important problem in chemical and materials sciences. In this study, protonated benzene (i.e., benzenium ion) and water clusters [BZH+Wn (where n = 1-6)] are selected as prototype models to understand the interfacial interactions and proton transfer mechanism between a carbonaceous surface and water molecules. The excess protons can localize in the vicinity of the hydrophobic-hydrophilic interface, and these clusters are stabilized by various kinds of noncovalent interactions. Calculations are carried out using ab initio (MP2) and density functional theory B3LYP methods to shed more light on geometries, energetics, and spectral signatures of the protonated species [H+(H2O)n] at the interfaces. These calculations revealed few low-lying isomers, which have not been reported earlier. Scrutiny of the results reveals that proton localization in the hydrophilic environment is more stable than the hydrophobic benzene π-cloud. Furthermore, the occurrence of an O-H+···π hydrogen bond significantly influences the O-H+···O interactions in the water clusters and also intensively affects the vibrational modes of the Eigen cation. Thus, the aromatic π-clouds can stabilize the Eigen cation and at the same time, a twisted form of Eigen (one O-H+···π → two O-H+···π) can enhance the proton transfer through the water chain via a Grotthuss-type mechanism. The vibrational spectra of these clusters reveal that there is a large red-shifted frequency for the O-H+···O, O-H+···π, and O-H···π modes of interaction. The energetic values and vibrational frequencies obtained from the B3LYP method are in close agreement with the MP2 level and experimental values, respectively.

Confinement of Candida Antarctica Lipase B in a Multifunctional Cyclodextrin-Derived Silicified Hydrogel and Its Application as Enzymatic Nanoreactor.

Supramolecular hydrogels with a three-dimensional cross-linked macromolecular network have attracted growing scientific interest in recent years because of their ability to incorporate high loadings of bioactive molecules such as drugs, proteins, antibodies, peptides, and genes. Herein, we report a versatile approach for the confinement of Candida antarctica lipase B (CALB) within a silica-strengthened cyclodextrin-derived supramolecular hydrogel and demonstrate its potential application in the selective oxidation of 2,5-diformylfuran (DFF) to 2,5-furandicarboxylic acid (FDCA) under mild conditions. The enzymatic nanoreactor was deeply characterized using thermogravimetric analysis, Fourier transform infrared spectroscopy, N2-adsorption, dynamic light scattering, UV-visible spectroscopy, transmission electron microscopy, scanning electron microscopy, and confocal laser scanning microscopy, while the reaction products were established on the basis of 1H nuclear magnetic resonance spectroscopy combined with high-performance liquid chromatography. Our results revealed that while CALB immobilized in conventional sol-gel silica yielded exclusively 5-formylfuran-2-carboxylic acid (FFCA), confinement of the enzyme in the silicified hydrogel imparted a 5-fold increase in DFF conversion and afforded 67% FDCA yield in 7 h and almost quantitative yields in less than 24 h. The hierarchically interconnected pore structure of the host matrix was found to provide a readily accessible diffusion path for reactants and products, while its flexible hydrophilic-hydrophobic interface was extremely beneficial for the interfacial activation of the immobilized lipase.